Avian myeloblastosis virus (AMV) contains 2 viral specific RNAs as shown by Northern hybridization analysis. These include the 7.5 Kb helper virus RNA and 7.0 Kb leukemogenic RNA. Both RNAs contain the "gag-pol" genes as shown by synthesis of the P180gag-pol polypeptide in in vitro translation studies. Since the RNAs appear to be homologous for the 5' 5.0 Kb, we have synthesized and cloned 3' ds CDNAs. These are currently being sequenced so as to further study the leukemogenic and helper nature of the AMV and MAV RNAs, respectively. Additionally, we have used AMV (MAU) cDNA probes to screen a quail-DNA recombinant library for integrated myelocytomatosis virus (MC29) sequences. A phage recombinant clone was identified and characterized by restriction enzyme, southern blot, and R-loop analysis. The clone contains a 9.2 Kb insert of which 4.0 Kb are viral sequences. This DNA contains all MC29 specific sequences as well as part of the "gag" and envelope structural genes. This DNA was also able to transform fibroblast cells in an in vitro infestivity assay. Further studies will include DNA sequencing of the MC29 transforming gene and biological experiments to illustrate the presence of a functional promotion region involved in viral RNA transcription.